From: Stefano Garzarella <sgarzare@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
Stefan Hajnoczi <stefanha@redhat.com>,
"David S. Miller" <davem@davemloft.net>,
virtualization@lists.linux-foundation.org,
Jason Wang <jasowang@redhat.com>,
kvm@vger.kernel.org
Subject: Re: [PATCH v4 3/5] vsock/virtio: fix locking in virtio_transport_inc_tx_pkt()
Date: Thu, 18 Jul 2019 09:43:04 +0200 [thread overview]
Message-ID: <CAGxU2F5PS8Ug3ei79ShVHOwLSXGYKwn3umvfvnhSFDs9pdvH2g@mail.gmail.com> (raw)
In-Reply-To: <20190717105056-mutt-send-email-mst@kernel.org>
On Wed, Jul 17, 2019 at 4:51 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Wed, Jul 17, 2019 at 01:30:28PM +0200, Stefano Garzarella wrote:
> > fwd_cnt and last_fwd_cnt are protected by rx_lock, so we should use
> > the same spinlock also if we are in the TX path.
> >
> > Move also buf_alloc under the same lock.
> >
> > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
>
> Wait a second is this a bugfix?
> If it's used under the wrong lock won't values get corrupted?
> Won't traffic then stall or more data get to sent than
> credits?
Before this series, we only read vvs->fwd_cnt and vvs->buf_alloc in this
function, but using a different lock than the one used to write them.
I'm not sure if a corruption can happen, but if we want to avoid the
lock, we should use an atomic operation or memory barriers.
Since now we also need to update vvs->last_fwd_cnt, in order to limit the
credit message, I decided to take the same lock used to protect vvs->fwd_cnt
and vvs->last_fwd_cnt.
Thanks,
Stefano
>
> > ---
> > include/linux/virtio_vsock.h | 2 +-
> > net/vmw_vsock/virtio_transport_common.c | 4 ++--
> > 2 files changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
> > index 49fc9d20bc43..4c7781f4b29b 100644
> > --- a/include/linux/virtio_vsock.h
> > +++ b/include/linux/virtio_vsock.h
> > @@ -35,7 +35,6 @@ struct virtio_vsock_sock {
> >
> > /* Protected by tx_lock */
> > u32 tx_cnt;
> > - u32 buf_alloc;
> > u32 peer_fwd_cnt;
> > u32 peer_buf_alloc;
> >
> > @@ -43,6 +42,7 @@ struct virtio_vsock_sock {
> > u32 fwd_cnt;
> > u32 last_fwd_cnt;
> > u32 rx_bytes;
> > + u32 buf_alloc;
> > struct list_head rx_queue;
> > };
> >
> > diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
> > index a85559d4d974..34a2b42313b7 100644
> > --- a/net/vmw_vsock/virtio_transport_common.c
> > +++ b/net/vmw_vsock/virtio_transport_common.c
> > @@ -210,11 +210,11 @@ static void virtio_transport_dec_rx_pkt(struct virtio_vsock_sock *vvs,
> >
> > void virtio_transport_inc_tx_pkt(struct virtio_vsock_sock *vvs, struct virtio_vsock_pkt *pkt)
> > {
> > - spin_lock_bh(&vvs->tx_lock);
> > + spin_lock_bh(&vvs->rx_lock);
> > vvs->last_fwd_cnt = vvs->fwd_cnt;
> > pkt->hdr.fwd_cnt = cpu_to_le32(vvs->fwd_cnt);
> > pkt->hdr.buf_alloc = cpu_to_le32(vvs->buf_alloc);
> > - spin_unlock_bh(&vvs->tx_lock);
> > + spin_unlock_bh(&vvs->rx_lock);
> > }
> > EXPORT_SYMBOL_GPL(virtio_transport_inc_tx_pkt);
> >
> > --
> > 2.20.1
next prev parent reply other threads:[~2019-07-18 7:43 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-17 11:30 [PATCH v4 0/5] vsock/virtio: optimizations to increase the throughput Stefano Garzarella
2019-07-17 11:30 ` [PATCH v4 1/5] vsock/virtio: limit the memory used per-socket Stefano Garzarella
2019-07-29 14:04 ` Michael S. Tsirkin
2019-07-29 15:36 ` Stefano Garzarella
2019-07-29 15:49 ` Michael S. Tsirkin
2019-07-29 16:19 ` Stefano Garzarella
2019-07-29 16:50 ` Stefano Garzarella
2019-07-29 19:10 ` Michael S. Tsirkin
2019-07-30 9:35 ` Stefano Garzarella
2019-07-30 20:42 ` Michael S. Tsirkin
2019-08-01 10:47 ` Stefano Garzarella
2019-08-01 13:21 ` Michael S. Tsirkin
2019-08-01 13:36 ` Stefano Garzarella
2019-09-01 8:26 ` Michael S. Tsirkin
2019-09-01 10:17 ` Michael S. Tsirkin
2019-09-02 9:57 ` Stefano Garzarella
2019-09-02 15:23 ` Michael S. Tsirkin
2019-09-03 4:39 ` Michael S. Tsirkin
2019-09-03 7:45 ` Stefano Garzarella
2019-09-03 7:52 ` Michael S. Tsirkin
2019-09-03 8:00 ` Stefano Garzarella
2019-07-29 16:01 ` Michael S. Tsirkin
2019-07-29 16:41 ` Stefano Garzarella
2019-07-29 19:33 ` Michael S. Tsirkin
2019-08-30 9:40 ` Stefano Garzarella
2019-09-01 6:56 ` Michael S. Tsirkin
2019-09-02 8:39 ` Stefan Hajnoczi
2019-09-02 8:55 ` Stefano Garzarella
2019-10-11 13:40 ` Stefano Garzarella
2019-10-11 14:11 ` Michael S. Tsirkin
2019-10-11 14:23 ` Stefano Garzarella
2019-10-14 8:17 ` Stefan Hajnoczi
2019-10-14 8:21 ` Jason Wang
2019-10-14 8:38 ` Stefano Garzarella
2019-07-17 11:30 ` [PATCH v4 2/5] vsock/virtio: reduce credit update messages Stefano Garzarella
2019-07-22 8:36 ` Stefan Hajnoczi
2019-09-03 4:38 ` Michael S. Tsirkin
2019-09-03 7:31 ` Stefano Garzarella
2019-09-03 7:38 ` Michael S. Tsirkin
2019-07-17 11:30 ` [PATCH v4 3/5] vsock/virtio: fix locking in virtio_transport_inc_tx_pkt() Stefano Garzarella
2019-07-17 14:51 ` Michael S. Tsirkin
2019-07-18 7:43 ` Stefano Garzarella [this message]
2019-07-22 8:53 ` Stefan Hajnoczi
2019-07-17 11:30 ` [PATCH v4 4/5] vhost/vsock: split packets to send using multiple buffers Stefano Garzarella
2019-07-17 14:54 ` Michael S. Tsirkin
2019-07-18 7:50 ` Stefano Garzarella
2019-07-18 8:13 ` Michael S. Tsirkin
2019-07-18 9:37 ` Stefano Garzarella
2019-07-18 11:35 ` Michael S. Tsirkin
2019-07-19 8:08 ` Stefano Garzarella
2019-07-19 8:21 ` Jason Wang
2019-07-19 8:39 ` Stefano Garzarella
2019-07-19 8:51 ` Jason Wang
2019-07-19 9:20 ` Stefano Garzarella
2019-07-22 9:06 ` Stefan Hajnoczi
2019-07-17 11:30 ` [PATCH v4 5/5] vsock/virtio: change the maximum packet size allowed Stefano Garzarella
2019-07-17 14:59 ` Michael S. Tsirkin
2019-07-18 7:52 ` Stefano Garzarella
2019-07-18 12:33 ` Michael S. Tsirkin
2019-07-19 8:29 ` Stefano Garzarella
2019-07-22 9:07 ` Stefan Hajnoczi
2019-07-22 9:08 ` [PATCH v4 0/5] vsock/virtio: optimizations to increase the throughput Stefan Hajnoczi
2019-07-22 9:14 ` Stefano Garzarella
2019-07-29 13:12 ` Stefan Hajnoczi
2019-07-29 13:59 ` Michael S. Tsirkin
2019-07-30 9:40 ` Stefano Garzarella
2019-07-30 10:03 ` Jason Wang
2019-07-30 15:38 ` Stefano Garzarella
2019-09-03 8:02 ` request for stable (was Re: [PATCH v4 0/5] vsock/virtio: optimizations to increase the throughput) Michael S. Tsirkin
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